Jon died last night. Just after reaching the rank of Lieutenant, both him and my good friend Seb got ambushed by a bunch of Thin Men and copped it. Soldier Me was back at base, nursing a grave injury after a run in with some particularly brutal Mechtoid, groaning in the infirmary with an equally bloodied and battered Carl. My girlfriend was the only one who made it out of that mission alive, largely thanks to a Hail Mary play that saw a fluke shot hit home, clearing a path to extraction. Jon and Seb and the sniper captain I'd named Starbuck weren't so lucky. Except it had nothing to do with luck, not really. I'd gotten them killed; I was the one who sent them running in too quickly after a time-sensitive resource. All those hours of careful progression and upgrading gone.

Welcome back, Commander. Everything you thought you knew has changed.

It's good to be sinking hours into XCOM again. Enemy Unknown was one of our favourite games of last year, and now, at a time when many are lamenting the absence of meaningful expansion packs like how they used to do, Firaxis have gone and dropped just such a big, fat expansion pack into the mix just in time for another run at Game of the Year.

Enemy Within presents the same outstanding turn-based strategy that you know and love, but with a host of additional maps, missions, customisation options, troops types, and enemies to face thrown into the equation. That might sound a little like a bit of a cop out, but nothing could be further from the truth. It's more like an outstanding director's cut -- a standalone package (on consoles, at least) that includes the original game, all of the DLC that's come out in the last year, as well as a host of new content. It's the gaming equivalent of those Lord of the Rings Extended Edition boxsets. And it's excellent.

The titular Enemy Within refers to a new foe, woven into the fabric of the original game's storyline, and providing branching narrative impetus, alternative perspectives, new research and engineering opportunities, and a slew of new missions. This time, there's a human element to the antagonist side of the story as well, with the mysterious terrorist cell network known as EXALT causing problems for you and the XCOM lot from around a third of the way through the game. EXALT are all about combining human biology and alien tech, and want the eradication of XCOM. Not only will they occasionally attempt direct action on the battlefield, but they'll also hack your financial accounts, and attempt the odd bit of cyberterrorism to spark panic across the world. If you don't find their cells and shut them down, widespread panic can lead to countries leaving the global council and abandoning the XCOM initiative. Lose too many supporting countries and it's game over.

In practical terms, MELD is the biggest addition to the game, being that it directly influences tactical decisions on the battlefield and asks questions of you as a base commander when it comes to prioritising research too. It's a volatile substance, this new material, and so it only lasts for a few turns on the battlefield, presenting commanders with an instant quandary: in a game that's all about careful, patient planning, and covering all of the angles, do you scramble to retrieve the MELD or maintain a methodical approach to ensure unit safety? It's another mechanism that taps straight into XCOM's fantastic balance of risk-vs.-reward, and it makes for some truly tense encounters.

Of course, there wouldn't be much point in me risking the lives of Jon, Carl, and myself if MELD didn't lay the groundwork for some very enticing possibilities indeed. This glowing, orangey substance is what turns XCOM into MECHS-COM! And, as we all know, mechs make everything better.

Secure enough MELD and your engineers will be able to build facilities for genetically modified troops as well as mechanised infantyr. Of course, there are separate modules for each, tying back into the delicate balance of base-building: when there are essential power generators, laboratories, workshops, and satellite uplinks to be housed, can you really risk stopping everything so you can churn out War Machine? The answer, of course, is yes. Of course you can, but you'd better make good use of them.

The gene mods turn your troops into Captain America-esque super soldiers, giving you stat boosts, health regeneration, and the ability to scale tall buildings in a single bound. They're pretty damn useful, but really they're just exaggerated versions of their regular counterparts. Useful, yes; but even they may come unstuck when staring down the business-end of a Mechtoid's arm cannon. Bring out the hulking Mechanized Exoskeleton Cybersuits (MECs), then! These surround your soldiers in swathes of delicious mechtastic armour, bestowing ridiculously heavy weaponry and a nice health boost upon them, and allowing you to more adequately bring the rain. Unfortunately, however, being an enormous mechanised powerhouse also makes you a terribly easy target. MEC soldiers are unable to take cover or use inventory items -- there's that risk/reward balance again.

XCOM Enemy Within presents you with a great feeling of empowerment and well-being the first time you crack out a MEC. It almost seems overpowered! What foe could possibly stop me with a handful of these at my disposal? you might cackle. And then you'll lose one -- whether to sustained onslaughts, dumb tactics, coming up against an enemy the same size, it doesn't really matter how it happens -- and you'll realise just how much they cost to build, maintain, and upgrade. You might even cry at the injustice of it all. I love that about Enemy Within: it lulls you into a false sense of empowerment and then slaps you in the face for getting ideas above your station, forcing you constantly to question and re-evaluate time and time again.

It's not all roses and joy, though. It's a little disappointing that EXALT are never really fully explained, so too that the morality of mucking about with human biology and the ethical implications of putting your soldiers under the knife and playing god is never really dealt with in greater depth. That being said, the modifications are all entirely optional. If there's a line that you as commander don't want to cross, that's up to you; I just feel it would perhaps have been nice to see the issue developed a little more in-game. There are more customisation options for your individual soldiers -- you can still create that all-female roster named after Marvel characters if you want -- chief among them being the ability to give them national accents to add to that sense of XCOM embodying a worldwide conflict. It's just a shame that there are only a handful, none of them include accents native to the British Isles, and I still can't put an afro on Captain Me. Elsewhere, the UI is as clean and brilliantly laid out as it ever was, although somehow the texture pop-in appears to be worse. On the Xbox 360, at least, it's everywhere, in each cutscene, in soldier customisation screens, even when you zoom in on rooms back at base.

But these are minor gripes really. Enemy Within takes an outstanding game we'd kind of learned how to beat, and shakes things up. Firaxis have sent experienced commanders back to the drawing board with this expansion, imbuing one of last year's best games with enough new versatility to warrant inclusion in next month's awards rosters. The new maps mean fewer occasions of reuse, and the new environments are expansive, challenging in terms of the cover opportunities (or lack thereof) that they present, often offering up potential in verticality that instills both excitement and caution.

The Short Version: Enemy Within is an improvement on an already outstanding game. It takes familiar systems, builds on top of them and challenges us in new ways, once again wearing our fingernails down to the bone and frazzling our nerves by making us second-guess each and every decision we make on and off the battlefield. It's bigger, deeper, and more challenging than ever before, forcing players to rethinktheir approaches, and expanding massively on replayability once more. Prepare to lose weeks to this game...AGAIN!